Field of the Invention
The present invention relates to coding and decoding of an audio signal, and in particular, to a method and apparatus for recovering a loss in a decoding process of the audio signal.
More particularly, the present invention relates to a recovering method for a case where a bit-stream from a speech and audio encoder is lost in a digital communication environment, and an apparatus using the method.
Related Art
In general, an audio signal includes a signal of various frequency bands. A human audible frequency is in a range of 20 Hz to 20 kHz, whereas a common human voice is in a frequency range of 200 Hz to 3 kHz. There may be a case where an input audio signal includes not only a band in which a human voice exists but also a component of a high frequency band greater than or equal to 7 kHz in which a human voice is difficult to exist.
Recently, with a network development and a growing user demand for a high-quality service, an audio signal is transmitted through various bands such as a narrow band (NB), a wide band (WB), and a super wide band (SWB).
In this regard, if a coding scheme suitable for the NB (having a sample rate of about 8 kHz) is applied to a signal of the WB (having a sampling rate of about 16 kHz), there is a problem in that sound quality deteriorates.
Further, if a coding scheme suitable for the NB (having a sampling rate of about 8 kHz) or a coding scheme suitable for the WB (having a sampling rate of about 16 kHz) is applied to a signal of the SWB (having a sampling rate of about 32 kHz), there is a problem in that sound quality deteriorates.
Accordingly, there is an ongoing development on a speech and audio encoder/decoder which can be used in various environments including a communication environment with respect to various bands ranging from the NB to the WB or the SWB or between the various bands.
Meanwhile, an information loss may occur in an operation of coding a speech signal or an operation of transmitting coded information. In this case, in a decoding operation, a process for recovering or concealing the lost information may be performed. As described above, if a loss occurs in an SWB signal in a situation where coding/decoding method optimized for each band is used, there is a need to recover or conceal the loss by using a different method other than a method of handling a WB loss.